Chapter 1: Understanding Kubernetes Secrets

In recent discussions, we have highlighted ConfigMaps as vital Kubernetes objects for storing various configurations for workloads. However, the inquiry arises: how do we handle sensitive information? This is where Kubernetes introduces the Secrets object, designed specifically for this purpose.

According to the official Kubernetes documentation, a Secret is defined as follows:

A Secret is an object that contains a small amount of sensitive data such as a password, token, or key. This information is typically too sensitive to be included in a Pod specification or within a container image. Utilizing a Secret allows developers to keep confidential data separate from application code.

Thus, Secrets are the recommended method for storing sensitive data. From a technical standpoint, they function similarly to ConfigMaps, allowing you to link them to environment variables, mount them within a pod, or manage credentials for various account types, including Service Accounts. The different categories of secrets include:

• Opaque: A general-purpose secret for configuration data or files.
• Service-Account-Token: Credentials for service accounts, deprecated as of Kubernetes 1.22.
• Docker-Registry Credentials: Used to authenticate with the Docker registry for image retrieval during deployment.
• Basic or SSH Auth: Secrets specifically for authentication tasks.
• TLS Secret: For managing TLS certificates.
• Bootstrap Secrets: For initializing resources securely.

So, is it secure to use Kubernetes Secrets for sensitive data? The answer varies, and indeed, this topic has sparked controversy. According to the Kubernetes documentation, several important points are raised:

Kubernetes Secrets are stored unencrypted by default in the API server's underlying data store (etcd). Anyone with API access can access or alter a Secret, as can anyone who has access to etcd. Furthermore, anyone authorized to create a Pod within a namespace can read any Secret in that namespace, including through indirect means like creating a Deployment.

The reality is that this default setup poses significant security risks. It resembles a categorization system rather than a secure handling method. To enhance security, Kubernetes recommends:

• Enabling encryption at rest for Secrets.
• Configuring Role-Based Access Control (RBAC) rules to restrict access to Secrets.
• Using RBAC to control who can create or replace Secrets.

However, these measures may not be sufficient, leading to the emergence of third-party and cloud solutions that address these concerns while offering additional features. Some notable options include:

• Cloud Key Management Systems: Major cloud providers offer their Secret Management solutions to enhance security. For instance, AWS has AWS Secrets Manager, Azure offers Azure Key Vault, and Google provides Google Secret Manager.
• Sealed Secrets: This project extends the concept of Secrets, offering enhanced security, particularly in a Configuration as Code context. It enables safe storage of these objects in repositories similar to other Kubernetes resource files. As stated, "The SealedSecret can only be decrypted by the controller running in the target cluster; even the original author cannot access the original Secret."
• Third-party Secrets Managers: Similar to cloud offerings, these provide independent solutions, with notable players like Hashicorp Vault and CyberArk Secret Manager.
• Spring Cloud Config: This tool facilitates secure storage of sensitive configuration data, such as passwords, while fulfilling the role of ConfigMap from a unified perspective.

In conclusion, this article aims to clarify the role of Secrets in Kubernetes, the associated security risks, and potential mitigations through alternative solutions that provide a more secure method for managing sensitive data.

Kubernetes Secret Management Explained - YouTube

This video delves into the intricacies of Kubernetes Secrets, discussing best practices for managing sensitive data within Kubernetes environments.

How to View Kubernetes Secrets Easily - YouTube

In this video, viewers will learn straightforward methods for accessing and managing Kubernetes Secrets effectively.